1. Field of the Invention
The present invention pertains to hermetically sealed, positive displacement compressors for use in refrigeration systems such as air conditioners, refrigerators and the like, and methods for assembling such compressors.
2. Description of the Related Art
Various types of positive displacement compressors have been used in refrigeration systems including, for example, reciprocating piston rotary vane, and scroll type compressors. In addition, multi-cylinder compressors, such as twin cylinder rotary compressors, are also known in the art. In general, twin cylinder rotary compressors comprise a housing containing a motor and a compression mechanism. The compression mechanism includes two cylinders, each defining a bore. The motor generally includes a crankshaft that extends through the two cylinders and has two eccentric portions, one located in the bore of each cylinder. The crankshaft is driven by the rotor of a motor having a stator which is connected to a power source via a terminal assembly. The motor rotates the crankshaft which, in turn, rotates the eccentric portions within the bores of the cylinders. Each eccentric portion has a roller piston rotatably mounted thereon, which revolves within the bore and cooperates with one or more sliding vanes and the cylinder wall to provide a pumping action for compressing a refrigerant within the cylinder bore.
Terminal assemblies, as described above, provide power to the stator. Prior terminal assemblies, generally, include a terminal body and a plurality of conductor pins. The terminal body is typically cup-shaped and is mounted in an aperture within the wall of the compressor housing. The terminal body has a plurality of holes each defined by a collar or annular lip. The conductor pins extend through and are secured within the holes by the annular lip and an insulating glass seal, which electrically insulates the pins from the terminal body. The interior ends of the conductor pins are connected to lead wires running to the stator and the exterior ends of the conductor pins are connected to a source of electrical power.
In order to prevent refrigerant leakage and accommodate the high pressures within the compressor, parts of the compressor are machined to extremely close tolerances and the compressor housing is hermetically sealed. In the case of the terminal assembly, the terminal body of the assembly is tightly fitted within an aperture of the compressor housing and is then sealed to the wall of the housing, typically by welding, brazing or the like. Ideally, terminal assemblies are assembled prior to mounting and welding the terminal body to the housing. However, the cup-shaped terminal body of prior terminal assemblies are often unable to withstand the high heat of welding or brazing. Consequently, the subsequent welding of the pre-assembled terminal assembly to the housing often results in damage to the terminal body, insulators and/or the conductive pins. In addition, the interior of compressors using carbon dioxide as a working fluid reaches substantially high temperatures and pressures. Prior terminal assemblies, particularly the mounting of the conductive pins within the holes of the terminal body, are often unable to withstand the high pressures created in these compressors. Therefore, a need remains for a terminal assembly that can better endure the welding process by which the terminal assembly is fixed to the compressor housing and is better able to withstand the higher pressures and temperatures experienced in a hermetic compressor using carbon dioxide as the refrigerant.
In addition, prior compressors often required extensive machining of the housing and the housing aperture to achieve a tight fit between the terminal body and the aperture of the housing. Such extensive machining adds difficulty, time and expense to the assembly process. Therefore a need remains for a terminal assembly that can be installed on the housing without the need for extensive machining of the housing.
Further, in certain twin cylinder rotary compressors the two cylinders are adjacent to one another and a partition plate is disposed between the two cylinders, thereby separating the bores of each cylinder from one another. The partition plate includes a central aperture through which the crankshaft is inserted. Assembling such a compressor can be significantly difficult, expensive and time consuming, because the partition plate must be mounted on the first cylinder after the first eccentric is positioned on the crankshaft, but before the second eccentric is positioned on the crankshaft. In addition, during assembly the partition plate slides down the shaft into position on top of the first cylinder. Such a method, quite possibly, lessens the ability to achieve the high tolerance and close fit necessary to withstand the pressures in the cylinders. Therefore, a need also remains for a compressor having a separator plate that, during assembly, can be easily installed such that the plate closely encircles the crankshaft between adjacent shaft eccentric portions and a method for assembling such a compressor.
The present invention provides a twin cylinder rotary compressor including first and second cylinders; a crankshaft having first and second eccentrics mounted thereon, the first eccentric disposed within the first cylinder, the second eccentric disposed within the second cylinder; and a separator plate disposed between the first and second cylinders and having a first piece and a complementary second piece. Each of the first and second pieces includes an interior surface defining a semi-circular recess. The interior surface and the semi-circular recess of the second piece is complementary to the interior surface and the semicircular recess of the first piece, respectively, such that the semi-circular recesses combine to form a circular bore, which closely captures a portion of the crankshaft located between the first and second eccentrics.
In a related aspect of the present invention, the separator plate includes a dowel having a first end received in a dowel hole in the interior surface of the first piece and a second opposite end received in an opposite dowel hole in the interior surface of the second piece, thereby securely joining the first and second pieces.
In another related aspect of the present invention, the separator plate includes a threaded fastener, which extends through a clearance aperture in the second piece and engages a threaded aperture defined in the interior surface of the first piece, thereby securely joining said first and second pieces. The fastener may include a head portion and the second piece may include an annular surface defining a notch. The clearance aperture is defined in the notch and the head portion of the fastener received in the notch.
In still a further aspect of the present invention, each of the first cylinder, second cylinder, and separator plate includes a set of clearance holes. Each of the sets of clearance holes are aligned with one another and each of the aligned clearance holes receive one of a plurality of fasteners.
In yet another related aspect of the present invention, the twin cylinder rotary compressor further includes a main bearing having a set of threaded holes in alignment with each of the set of clearance holes of the first cylinder, second cylinder, and separator plate. Each one of the aligned threaded holes receives one of the plurality of fasteners, thereby mounting the first cylinder, second cylinder, and two-piece separator onto the main bearing.
The present invention further provides a twin cylinder rotary compressor including first and second cylinders and a separator plate disposed between the first and second cylinders. The separator plate includes a first piece and a complementary second piece, each of the first and second pieces including an interior surface defining a semi-circular recess. The interior surface and the semi-circular recess of the second piece are complementary to the interior surface and the semicircular recess of the first piece, respectively, such that the semi-circular recesses combine to form a circular bore.
The present invention also provides a separator plate for a twin cylinder rotary compressor having first and second cylinders, and a crankshaft extending through the first and second cylinders and having first and second eccentrics mounted thereon. The separator plate includes a first piece and a complementary second piece. The first piece and the second complementary piece disposed between the first and second cylinders and each of the first and second pieces includes an interior surface defining a semi-circular recess. The interior surface and the semi-circular recess of the second piece is complementary to the interior surface and the semicircular recess of the first piece, respectively, such that the semi-circular recesses combine to form a circular bore. The circular bore is adapted to closely encompass a portion of the crankshaft located between the first and second eccentrics.
Furthermore, the present invention provides a method of assembling a twin cylinder rotary compressor including the step of assembling a compressor sub-assembly by mounting a second cylinder on a main bearing; inserting a crankshaft having first and second eccentrics mounted thereon, into the second cylinder and main bearing; positioning first and second pieces of a separator plate on the second cylinder and around the crankshaft such that a semicircular recess in an interior surface of the first piece pairs with a semicircular recess in an interior surface of the second piece to form a bore, and the bore closely encompasses a portion of the crankshaft located between the eccentrics; and mounting a first cylinder about the crankshaft and on the separator plate.
In a related aspect of the present invention, the step of assembling a compressor sub-assembly includes fastening the first and second pieces of the separator plate together by inserting one end of a dowel into a dowel hole in the interior surface of the first piece; and inserting an opposite end of the dowel into an opposite dowel hole in the interior surface of the second piece.
In another related aspect of the present invention, the step of assembling a compressor sub-assembly includes fastening the first and second pieces of the separator plate by inserting a threaded fastener through a clearance aperture in the second piece and engaging the fastener to a threaded aperture defined in the interior surface of the first piece.
Still further, the method of assembly according to the present invention may also include the step of mounting the compressor sub-assembly to a motor by fastening a stator of the motor to the main bearing of the sub-assembly.
In another aspect of the present invention, the method of assembly includes step of mounting the compressor sub-assembly in a housing by heat-expanding the housing, inserting the compressor sub-assembly into the housing and shrink-fitting the housing onto the compressor sub-assembly.
The present invention also provides a method of assembling a twin cylinder rotary compressor including the steps of assembling a compressor sub-assembly by mounting a second cylinder on a main bearing, positioning first and second pieces of a separator plate on the second cylinder such that a semicircular recess in an interior surface of the first piece pairs with a semicircular recess in an interior surface of the second piece to form a bore; and mounting a first cylinder on the separator plate; attaching the sub-assembly to a motor to produce a motor-compressor assembly; and mounting the motor-compressor assembly in a housing.